Method of forming a tubular member with flange

ABSTRACT

The method of forming a flanged tubular member is accomplished by sizing the tubular blank to the largest cross section circumferential measure of the desired end product and then using a hydro-forming die and process to expand any excess circumferential measure into a flange defining portion of the die cavity to thereby enable the formation of a cross section of lesser cross sectional circumferential measure than the largest cross section. The flange may be trimmed as desired to shorten the length of the flange, in which case, welding or other suitable attachment process may be employed to join the flanges together to strengthen the tubular member.

The invention relates to forming a shaped tubular member and moreparticularly provides a tubular member having a flange.

BACKGROUND OF THE INVENTION

It is known to form the cross sectional profile of a tubular member by ahydro-forming process in which a fluid filled tubular blank is placedwithin a die and then the die is closed so that the tubular blank ispinched within the die. Fluid pressure is then increased inside thetubular member to expand the blank outwardly against the die cavity toprovide a tubular product having a die formed cross sectional profile.The tubular product may have different cross sectional profiles alongthe length thereof.

A disadvantage of the aforedescribed method of forming a tubular memberresides in the fact that the circumferential measure of the crosssection must be of generally the same dimension all along the length ofthe tubular member. The prior art has recognized that thecircumferential expansion of the blank is limited to about two to fivepercent when using readily available grades of tubular steel. Expansionsof circumference of up to about 20 percent can be performed if thetubular blank is of fully annealed tubular steel. This limitation in theextent of permissible expansion, limits the potential for formingtubular members having differing cross sectional circumferential measurealong the length of the tubular member.

It would be desirable to provide a forming method which would enable themanufacture of a tubular member which would have substantially differentcross section circumferential measure along the length of the tubularmember.

The aforedescribed tubular members are particularly useful in themanufacture of vehicle bodies. For example, in U.S. Pat. No. 4,945,682it is shown that such a tubular member may be employed to reinforce avehicle door molded of synthetic resin. In many vehicle structures, suchas doors, it would be desirable to provide such a tubular member with aflange to facilitate the attachment thereto of weather strips or othervehicle body components.

Therefore it would be desirable to provide a method of forming anintegral flange on a hydro-formed tubular member.

SUMMARY OF THE INVENTION

According to the invention, the method of forming a flanged tubularmember is accomplished by sizing the tubular blank to the largest crosssection circumferential measure of the desired end product and thenusing a hydro-forming die and process to expand any excesscircumferential measure into a flange defining portion of the die cavityto thereby enable the formation of a cross section of lesser crosssectional circumferential measure than the largest cross section. Theflange maybe trimmed as desired to shorten the length of the flange, inwhich case, welding or other suitable attachment process may be employedto join the flanges together to strengthen the tubular member.

In particular, the method comprises the steps of:

providing a tubular blank having a cross sectional circumferentialmeasure;

positioning the blank between open die halves mating with one another todefine a tubular cross section portion having a height substantiallyequal to twice the wall thickness of the tubular blank and a flangecavity portion;

applying at least nominal internal hydraulic pressure to the blank;

progressively closing the die halves to progressively deform the tubularmember within the tubular cavity portion and progressively expel thetubular member into the flange cavity portion to define a flangecomprised of wall portions of the tubular member engaging one another;

increasing the hydraulic pressure to expand and conform the tubularmember to the tubular cavity portion;

separating the die halves;

and removing the blank from the die.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, objects and advantages of the invention willbecome apparent upon consideration of the description of the preferredembodiment and the appended drawings in which:

FIG. 1 shows a tubular blank which has been bent to the desired shape ofthe finished product;

FIG. 2 shows the tubular member hydro-formed to a desired cross sectionand having a flange extending along at least a portion of the lengththereof;

FIG. 3 shows the finished article with the flange having been trimmedback to a desired length;

FIG. 4 is a cross sectional view of the tubular blank of FIG. 1 placedbetween the halves of a die set;

FIG. 5 is a view showing partial closing of the die set so that thefluid pressure trapped within the tubular member forces excess metalinto flange forming portion of the dies;

FIG. 6 is a view showing the die set having been completely closed withthe fluid pressure having displaced wall portion to define a flange andshowing the remaining wall having been irregularly impressed within theremaining cavity of the die set;

FIG. 7 shows the tubular member having been expanded and conformed tothe shape of the die cavity by hydraulic pressure applied within thetubular member;

FIG. 8 shows the die set opened to permit removal of the tubular membertherefrom;

FIG. 9 shows the finished tubular member placed in a trimming die;

FIG. 10 shows the trimming die closed to trim the flange; and

FIG. 11 shows the welding together of the flanges by a resistance spotwelder.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 there is shown a tubular blank 10 of circular crosssection which has been bent into a L-shape through a suitable bendingprocess such as mandrel bending or stretch bending.

FIG. 2 shows an intermediate step in the forming of a tubular memberfrom the blank 10 and FIG. 3 shows the finished tubular member 11manufactured according to the steps shown in FIGS. 4-11 and describedhereinafter.

As shown in FIG. 4 the blank 10 of FIG. 1 is placed in a die setcomprised of upper die half 12 and lower die half 14. The upper die 12includes a tubular forming cavity portion 16 and a flange forming cavityportion 18. Likewise, the lower die 14 has a tubular forming cavityportion 20 and a flange forming cavity portion 22. It will be understoodthat the combined cross sectional circumferential measure of the tubularforming cavity portions 16 and 20 and the length of the flange formingcavity portions 18 and 22 total up to generally equal to or slightlygreater than the cross section perimeter length of the blank 10.

The ends of the tubular blank 10 are sealed and hydraulic fluid ispumped into the tubular blank 10 under pressure. The upper die half 12and lower die half 14 are progressively closed as shown in FIG. 5 sothat the blank 10 is progressively flattened and the pressurized fluidcaptured therein expands the walls of the tubular blank 10 into thecavities of the die. In particular, as seen in FIG. 5, the tubular blank10 is expelled and forced to migrate laterally into the flange formingcavity portions 18 and 22.

As seen in FIG. 6, the die halves 12 and 14 are fully closed upon oneanother with the tubular blank being tightly clamped between the diehalves 12 and 14 to define a flange structure 24, the remainder of thetubular blank 10 having been irregularly bowed or dished inwardly.During this closing of the die halves as shown in FIGS. 4, 5, and 6, arelatively constant hydraulic pressure may be maintained within thetubular blank by incorporating a pressure relief valve into the sealenclosing the ends of the tubular blank 10 so that hydraulic fluid maybe forced from the tubular blank 10 as it collapses. As best seen inFIG. 6, the combined height of the flange forming cavity portions 18 and22 is equal to twice the wall thickness of the tubular blank 10 so thatthe walls of the tubular blank 10 forming the flange structure 24 engagewith one another.

Once the die is closed, the blank tube 10 is then expanded to the finalcross sectional profile of FIG. 7 by increasing the hydraulic pressuresufficient to exceed the yield limit of the tubular blank 10 so that thetubular blank 10 is forced into conformity with the tubular formingcavity portions 16 and 20 of the die halves.

FIG. 8 shows the die halves being opened to permit removal of the formedtube from the dies.

FIGS. 4 through 8 show a particular cross section through the tubularmember, it being understood that differing cross sections may beprovided at different points along the length of the tube. For example,as shown in FIG. 2, the tubular member 26 may have the tubular portionthereof gradually increasing in dimension while the flange 24 of thetube member 26 progressively diminishes in dimension. In this respect itwill be understood that the dies are designed to provide the desiredcross sectional tubular shape with any remaining unused wall portion ofthe tube then relegated to being displaced into the flange portion ofthe tubular member.

Subsequent to forming the product to the condition shown in FIG. 3, itwill understood that additional manufacturing processes may be applied,for example flanging or shaping the ends of the tubes as desired withinthe teachings of the prior art.

The finished tubular member 26 may be assembled into a vehicle body withthe flange 24 employed to mount a weather strip or some other desiredvehicle component. FIGS. 9, 10 and 11 show that any excess part of theflange 24 can be trimmed from the tubular member 26. In particular, FIG.10 shows the formed tubular member 26 of FIG. 8 placed in a trim diecomprised of an upper die half 30 and a lower die half 32. The upperhalf carries a suitably hardened shear insert 34 which is aligned toprecisely overlap a shear block 36 mounted on the lower die half 32.

Accordingly, as the die halves 30 and 32 are closed relative oneanother, the shear insert 34 cuts away the portion of the flange 24which overhangs the shear block 36.

FIG. 11 shows spot welding electrodes 40 and 42 which apply a spot weldbetween the walls of flange 24 to strengthen and rigidify the tubularmember 26. It will be understood that other welding or suitableattaching methods may be employed to join wall of the flange 24together.

Thus it is seen that the tubular member may be manufactured to includean integral flange, and furthermore the tubular member may have crosssections of differing circumferential measure with the excess materialpushed into the flange portion of the tubular member. In addition, theflange portion may be trimmed to desired length.

Therefore in designing the die cavity for use in practicing theaforedescribed method, it will be understood that the totalcircumferential measure of the die cavity will remain constant and thatthe shape of the cross section will be varied along the length of thetubular member by varying the proportion of wall circumferential devotedto forming the tubular portion and the flange portion. For example, ifit is desired to provide a larger tubular portion, the length of theflange forming portion is correspondingly reduced. In particular, itwill be noted that the length of the flange structure will be generallyhalf the difference between the cross sectional circumferential measureof the tubular blank 10 as measured before the forming operation hasbegun, and the cross sectional circumferential measure of the tubularportion which is desired to be obtained at that particular point alongthe length of the tubular member.

Accordingly by applying the above described method it will beappreciated that the circumferential measure of a deformed tubularmember may have substantially greater variations in cross section alongthe length than permitted by the prior art.

The embodiments of the invention in which an exclusive property orprivilege is claimed we defined as follows:
 1. Method of forming aflanged tubular member comprising the steps of:providing a tubular blankhaving a cross sectional circumferential measure; positioning the blankbetween open die halves mating with one another to define a tubularcross section portion and a flange cavity portion having a heightsubstantially equal to twice the wall thickness of the tubular blank;applying at least nominal internal hydraulic pressure to the blank;progressively closing the die halves to progressively deform the tubularmember within the tubular cavity portion and progressively expel thetubular member into the flange cavity portion to define a flangecomprised of wall portions of the tubular member engaging one another;increasing the hydraulic pressure to expand and conform the tubularmember to the tubular cavity portion; separating the die halves; andremoving the blank from the die.
 2. The method of claim 1 comprising thefurther step of trimming the flange.
 3. The method of claim 2 comprisingthe further step of welding together the wall portions defining thetrimmed flange.
 4. A method of forming a tubular member having differingcross sections along the length thereof and differing circumferentialmeasure at said differing cross sections, comprising the stepsof:providing a tubular blank having a uniform cross sectionalcircumferential measure; positioning the blank between open die halveseach having a tubular cavity portion mating with the other to define atubular cross section of the desired differing cross section and eachhaving a flange cavity portion mating with the other to define a crosssection of generally twice the wall thickness of the blank and lengthequal to half the difference between the cross sectional circumferentialmeasure of the blank and the cross sectional circumferential measure ofthe desired differing cross section at that point along the length ofthe tubular member; applying at least nominal internal hydraulicpressure to the blank; progressively closing the die halves toprogressively deform the tubular member within the tubular cavityportion and progressively expel the perimeter wall portion of thetubular member into the flange cavity portion to thereby define theflange; increasing the hydraulic pressure to expand and conform thetubular member to the tubular cavity portion to thereby define thedesired differing cross sections; separating the die halves; removingthe blank from the die; and trimming the flange as desired.
 5. Themethod of claim 4 comprising the further step of welding together thewall portions defining the trimmed flange.